That would potentially wreck a lot of ecosystems, especially if it's eliminating a water source. You'd have to work pretty hard to maintain suspension of disbelief, and besides, cacti don't live exclusively in deserts.

Alright. You know, I realized that "moon cactus" seems a bit cliché, considering how many SCPs there are that have to with the moon. How about instead, there's a group of cacti on a different planet? I mean, almost all of the other planets in our solar system are just huge deserts anyway. I should look up which one of the planets don't have an SCP about them.

Also, maybe the cacti move sometimes from where they were. In fact…how about a planet hopping group of cacti? One time they're on Mars, a few weeks (or days or months, doesn't really matter) later, they're on Venus, later on Neptune, maybe even on the surface of the sun.

Even better, it's nickname could be Lunar anywhere cacti, as in, they may have first been discovered on the moon (or somewhere else) and then disappeared to another planet/moon.

Maybe, it could have first been classified as an extranormal event. Maybe, "a group of cacti were seen on the surface on Jupiter. After a week, they had disappeared," but later, they found them on Venus.

I don't know about Jupiter, Jupiter is just a ball of gas… Venus, Mercury, or if you're looking at dwarf planets, Pluto/Eris. if you want to stick with the moon idea, why not go with one of Jupiter's moons, or Saturn's moons? There's a lot of potential in our solar system, don't waste it on Jupiter :/